In target shooting using a firearm, especially where the distance between the shooter and the target is large, e.g., 20 yards or more, it is difficult for the shooter to see the point at which his bullet punctures the target. At these longer distances, in order to see the points of impact on an ordinary target, the shooter must use a spotting telescope, approach the target, or utilize a target-moving apparatus to move the target toward the firing line for inspection.
Another way to make the point of impact visible is to incorporate into the target a coloring material that is dispersed by impact, enhancing the visibility of the point of impact. A “self-marking” target, utilizing a coloring material for this purpose is described in U.S. Pat. No. 3,330,561, granted Jul. 11, 1967. In the system described in U.S. Pat. No. 3,330,561, an array of receptacles, each containing a colored solid or liquid material is disposed behind a porous target sheet having a protective layer on its back surface. When the porous target sheet is struck by a bullet, the colored material in the receptacle behind the point of impact is released through the bullet hole formed in the target sheet and the protective layer, and absorbed by the target sheet in the vicinity of the point of impact, making the point of impact immediately visible to the shooter. In an alternative embodiment, instead of using a colored material, the receptacles contain a reactant liquid that combines chemically with a substance previously absorbed in the pores of the target sheet, producing a visible color change in the vicinity of the point of impact.
A problem with the target described in U.S. Pat. No. 3,330,561 is that size of the array of receptacles for coloring material or reactant is the same as the size of the target. Large amounts of coloring material or reactant are never used, especially if the shooter is sufficiently skilled to shoot in a tight pattern.